This disclosure generally relates to side bearings for controlling rocking dynamics, rolling dynamics, curving negotiation, and high speed stability of a railroad freight car.
A typical “three-piece” railroad car truck comprises two parallel side frames connected by a bolster laterally spanning the distance between the side frames. A car body sits atop the bolster with, among other things, one or more side bearings positioned between the bolster and the car body. The typical bolster-car body interconnection allows the car body to pivot about a bowl at the center of the bolster, with the side bearings frictionally engaging the underside of the car body and working to counteract the tendency of the car body to “hunt,” oscillate, roll, or otherwise move in an uncontrolled manner with respect to the bolster.
A typical constant contact-type side bearing includes a base, one or more resilient elements, and a cap. The base retains the resilient elements on the bolster, while the cap overlays the resilient elements to engage a wear plate on the underside of the car body. The resilient elements bias the cap into constant engagement with the wear plate to prevent the car body from moving free of the resisting influence of the side bearing. A variety of different side bearings are known, including those described in U.S. Pat. No. 4,130,066 to Mulcahy; U.S. Pat. No. 5,806,435 to Pitchford; and U.S. Pat. No. 7,325,499 to Jensen et al., all of which are hereby incorporated herein by reference.